Mobility management system by distributed mobile IP

ABSTRACT

In the Mobile IPv4 network in the present invention, FA control servers ( 7   a,    7   b ) that process only Mobile IP signaling, and IP tunnel routers ( 8   a,    8   c ), being an IP tunnel endpoint, which also function as a default router with respect to a mobile node MN, form an FA function (referred to as a virtual FA). Further, an HA control server ( 9 ) that processes only Mobile IP signaling, and an IP tunnel router ( 8   b ), being an IP tunnel endpoint, form an HA function (referred to as a virtual HA). Here, the relation between the FA control servers ( 7   a,    7   b ) and the IP tunnel routers ( 8 a,  8   c ), and the relation between the HA control server ( 9 ) and the IP tunnel router ( 8   b ) are such that the former is a Media Gateway Controller (MGC) and the latter is a Media Gateway (MG). The FA control server ( 7   a ) notifies a mobile node MN ( 2 ) of the own address as an FA care-of address, in the form of a regular broadcast or query response. The IP tunnel router ( 8   a ) constituting the virtual FA notifies the mobile node MN ( 2 ) of an address, being a default router, in the form of a regular broadcast or query response.

TECHNICAL FIELD

The present invention relates to a mobility management technique formobile packet communication.

BACKGROUND ART

Mobile IP (RFC 2002) has been suggested in the Internet Engineering TaskForce (IETF), as a method for maintaining communication withoutinterrupting the session by a mobile node MN, when a terminal having anIP address moves across a subnet (see “RFC 2002: IP Mobility Support” byC. Perkins, IETF Internet Draft, 1996/10, pages 8 to 11).

This concept is explained in detail in “Detailed Mobile IP” (see“Detailed Mobile IP” by James D. Solomon, Pearson Education Japan, Jul.27, 1998, pages 57 to 77).

FIG. 13 illustrates an example of communication using the Mobile IP.Reference sign 1 a denotes an IP subnetwork, 1 b denotes an IPsubnetwork belonging to a subnet different from the IP subnetwork 1 a, 2denotes a mobile node MN mounted with the Mobile IP, 3 a and 3 b denoteaccess points accommodating the mobile node, 4 denotes a Mobile IPforeign agent (FA), 5 denotes a home agent (HA) controlling the positionof the mobile node 2 as the IP address of the FA, and 6 denotes acommunication partner node (CN) communicating with the mobile node.

In the Mobile IP, the HA 5 is arranged in the home domain of the mobilenode (MN) 2, and an IP address belonging to this home domain(hereinafter, “home address”) is allocated to the mobile node (MN) 2 ina fixed manner. The FA address at which the mobile node (MN) 2 ispresent is controlled by the HA 5 as a position of the mobile node (MN)2. Therefore, the mobile node (MN) 2 registers in the HA a new FAaddress (referred to as an FA care-of address) as an address to whichthe mobile node (MN) 2 moves, via the new FA, at a timing of detectingthat the mobile node (MN) 2 moves from under a supervision of the old FAto under the new FA.

When the CN 6 transmits an IP packet to the mobile node (MN) 2, the HA 5controlling the FA care-of address of the mobile node (MN) 2 capturesthe packet addressed to the home address of the mobile node (MN) 2, andtransfers the captured IP packet to the registered FA 4 through an IPtunnel. The transfer through the IP tunnel stands for encapsulating theIP packet received by the HA with an IP header having:

-   -   a sender address: IP address of the HA 5, and    -   a destination address: FA care-of address,        and transferring it to the FA. Upon reception of the        encapsulated IP packet, the FA 4 takes out the original IP        packet therefrom, and transfers it to the mobile node (MN) 2. By        this mechanism, movement transparency of the mobile node (MN) 2        is realized in the Mobile IP.

When the mobile node (MN) 2 obtains the IP address in the subnet at themoving destination, the mobile node (MN) 2 can directly register this IPaddress (referred to as a collocated care-of address) as an address towhich the mobile node (MN) 2 moves, in the HA 5. In this case, the IPtunnel is set not between the FA 4 and the HA 5, but between the mobilenode (MN) 2 and the HA 5.

The IP packet transmission from the mobile node (MN) 2 to the CN 6 isperformed by transmission via a normal routing or by transmission viathe IP tunnel.

In the conventional configuration, since the FA and the HA havefunctions of signaling processing of the Mobile IP and IP tunneltransfer processing of a user packet, the load concentrates on theseparts.

Generally, the next-generation network has a network configuration inwhich a control plane for performing signaling processing, and a userplane for performing user packet processing are separately mounted. Insuch a distributed network, independent development of the signalingprocessing and the user packet processing, realization of scalability ofeach plane, realization of load balancing on each plane, low cost of thegeneral-purpose user packet processor, and high performance and low costby realizing the signaling processing on a general-purpose computer areexpected. However, the Mobile IP does not assume such a distributednetwork, and hence expansion to the next-generation network isdifficult.

Particularly, in the Mobile IP, the FA assumes a message informing theown address, and the mobile node MN regards the sender IP/MAC addressesin this message as the FA, to perform position registration signaling,and also regards it as a default router to transmit the user data. Thisindicates that one IP address is used for both signaling and user packetprocessing, and hence the control plane and the user plane cannot beseparated.

Further, it is not specified how the address information informed by theposition registration from the mobile node MN to the HA is handled, whenthe control plane and the user plane are separated.

With regard to the procedure when the mobile node MN does not know theaddress of the HA control server, it is not specified how it is changed,when the control plane and the user plane are separated.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to at least solve the problemsin the conventional technology.

A mobility management system according to one aspect of the presentinvention uses a distributed Mobile IP, in a Mobile IP network whichallows a mobile node while moving to hold a current communicationsession. The mobility management system includes a foreign agent controlserver that is located in a first subnet where the mobile node islocated, performs Mobile IP signaling; a first IP tunnel router that islocated in the first subnet, and performs IP tunnel transfer; a homeagent control server that is located in a second subnet where the mobilenode is located, and performs Mobile IP signaling; and a second IPtunnel router that is located in the second subnet, and performs IPtunnel transfer. The foreign agent control server and the first IPtunnel router constitute a virtual foreign agent. The home agent controlserver and the second IP tunnel router constitute a virtual home agent.

A mobility management system according to another aspect of the presentinvention uses a distributed Mobile IP, in a Mobile IP network whichallows a mobile node while moving to hold a current communicationsession. The mobility management system includes an access routercontrol server that is located in a first subnet where the mobile node(MN) is located, performs Mobile IP signaling; a first IP tunnel routerthat is located in the first subnet, and performs IP tunnel transfer; ahome agent control server that is located in a second subnet where themobile node is located, and performs Mobile IP signaling; and a secondIP tunnel router that is located in the second subnet, and performs IPtunnel transfer. The access router control server and the first IPtunnel router constitute a virtual access router. The home agent controlserver and the second IP tunnel router constitute a virtual home agent.

The other objects, features, and advantages of the present invention arespecifically set forth in or will become apparent from the followingdetailed descriptions of the invention when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of a Mobile IP network in which acontrol plane and a user plane are separated, being the prerequisite inthe first to the eighth embodiments of the present invention;

FIG. 2 illustrates a control flow of a distributed Mobile IP in thefirst embodiment of the present invention;

FIG. 3 illustrates the operation at the time of receiving an ICMPmessage in a mobile node (MN) 2 in the first, and the third to the fifthembodiments of the present invention;

FIG. 4 illustrates a processing flow of each apparatus at the time ofexecuting position registration of the distributed Mobile IP in thefirst embodiment of the present invention;

FIG. 5 illustrates a control flow of the distributed Mobile IP in thesecond embodiment of the present invention;

FIG. 6 illustrates a processing flow of each apparatus at the time ofexecuting position registration of the distributed Mobile IP in thesecond embodiment of the present invention;

FIG. 7 illustrates a flow of IP address notification of an FA controlserver and an IP tunnel router in the distributed Mobile IP in the thirdembodiment of the present invention;

FIG. 8 illustrates a flow of IP address notification of the FA controlserver and the IP tunnel router in the distributed Mobile IP in thefourth embodiment of the present invention;

FIG. 9 illustrates a control flow of the distributed Mobile IP in thefifth embodiment of the present invention;

FIG. 10 illustrates a processing flow of each apparatus at the time ofexecuting position registration of the distributed Mobile IP in thefifth embodiment of the present invention;

FIG. 11 illustrates a flow for obtaining the IP address of an HA controlserver in the distributed Mobile IP in the sixth embodiment of thepresent invention;

FIG. 12 illustrates a flow for obtaining the IP address of the HAcontrol server in the distributed Mobile IP in the eighth embodiment ofthe present invention; and

FIG. 13 illustrates the operation of the conventional Mobile IP network.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

FIG. 1 is a configuration diagram of a Mobile IPv4 network in the firstembodiment.

In FIG. 1, a foreign agent function (hereinafter, “FA function”)includes FA control severs 7 a and 7 b for performing only Mobile IPsignaling processing, and IP tunnel routers 8 a and 8 c for performingonly transfer processing of user data. A home agent function(hereinafter, “HA function”) includes an HA control server 9 forperforming only Mobile IP signaling processing and an IP tunnel router 8b for performing only the transfer processing of user data. The otherconfiguration is the same as that in FIG. 13.

FIG. 2 is a conceptual diagram illustrating the entire operation of theMobile IP in the network in illustrated FIG. 1, FIG. 3 illustrates theoperation at the time of receiving an ICMP message by a terminal, andFIG. 4 illustrates an operation flow of each apparatus at the time ofposition registration.

In this embodiment, the FA control server 7 a regularly broadcasts theown address of the FA control server as an FA care-of address, as shownby reference numeral 10 in FIG. 2. The message is a kind of the ICMPmessage, and is referred to as a distributed mobile agent advertisement.In order to notify a mobile node (MN) 2 that the storage network is thedistributed Mobile IP network, a code field value and the like in themessage is changed with respect to a normal mobile agent advertisement.

As illustrated in FIG. 3, the mobile node (MN) 2 receives thedistributed mobile agent advertisement, and recognizes the sender MAC/IPaddresses thereof as the FA control server 7 a, being the destination ofthe position registration signaling. The distributed mobile agentadvertisement may be transmitted as a response to an advertisementrequest message from the mobile node MN.

The IP tunnel router 8 a regularly broadcasts the IP address, being adefault router, with respect to the mobile node MN, as shown byreference numeral 11 in FIG. 2. The message is a normal ICMP routeradvertisement message. As illustrated in FIG. 3, the mobile node (MN) 2receives a router advertisement, and recognizes the sender MAC/IPaddresses as the IP tunnel router 8 a, being the destination of a userpacket. The router advertisement may be transmitted as a response to anadvertisement request message from the mobile node MN.

The mobile node MN can respectively recognize the FA control server onthe control plane and the IP tunnel router on the user plane, byrespectively receiving the distributed mobile agent advertisement andthe ICMP router advertisement.

The mobile node MN having recognized the IP addresses of the FA controlserver 7 a and the IP tunnel router 8 a creates a position registrationmessage including the IP address information of a known HA controlserver 9, and transmits it to the MAC/IP addresses of sender of thedistributed mobile agent advertisement (reference numeral 13 in FIG. 2).The FA control server 7 a receives the position registration message,and obtains the care-of address, being an endpoint of the IP tunnel, inthe IP tunnel router 8 a after having scrutinized the message. Theaddress may be different from the default router address of the IPtunnel router 8 a, and this address is determined by referring to the IPtunnel router 8 a. However, when the FA control server 7 a controls theresource of the IP tunnel router 8 a, the address may be determinedindependently, without referring to the IP tunnel router 8 a.

The FA control server 7 a sets the obtained IP tunnel endpoint addressin the IP tunnel router 8 a as a care-of address in the positionregistration message, and transfers the position registration messagewith respect to the address of the HA control server 9 notified from themobile node MN (reference numeral 14 in FIG. 2). The HA control server 9having received the position registration message obtains an address asthe endpoint of the IP tunnel in the IP tunnel router 8 b, after havingstored the IP tunnel information in the message. This address isdetermined by referring to the IP tunnel router 8 b. However, when theHA control server 9 controls the resource of the IP tunnel router 8 b,the address may be independently determined without referring to the IPtunnel router 8 b. The HA control server 9 notifies the IP tunnel router8 b of the IP tunnel endpoint of the opposing IP tunnel router 8 a.

The HA control server 9 sets the IP tunnel endpoint address in theobtained IP tunnel router 8 b in the position registration responsemessage as a HA address, and transmits it to the FA control server 7 a(reference numeral 15 in FIG. 2). The FA control server 7 a establishesan IP tunnel (denoted by reference numeral 16 in FIG. 2) between the IPtunnel routers 8 a and 8 b by notifying the IP tunnel router 8 a of theIP tunnel endpoint in the tunnel router 8 b. Thereafter, the FA controlserver 7 a transfers the position registration response message to themobile node (MN) 2 (reference numeral 17 in FIG. 2).

By a series of operation, as illustrated in FIG. 4, a user data path isformed via the IP tunnel routers 8 a and 8 b.

The FA function virtually includes the FA control server and the IPtunnel router, and the HA function virtually includes the HA controlserver and the IP tunnel router. Since the FA control server notifiesthe mobile node (MN) 2 of the own address as the FA care-of address, andthe IP tunnel router constituting the FA function notifies the mobilenode (MN) 2 of the IP address of the default router, the mobile node(MN) 2 can recognize the FA control server and the IP tunnel routerrespectively individually. Therefore, a Mobile IP network in which thecontrol plane and the user plane are separated totally from the mobilenode (MN) 2 to the HA can be constructed. In the Mobile IP network inwhich the control plane and the user plane are separated, the loadbalancing between the control plane and the user plane becomes possible,thereby enabling independent correspondence to upgrade of signaling andspeed-up of the tunnel processing. As a result, an optimized system canbe constructed. The high-speed system can be provided at low cost, byconstructing the control plane on a general-purpose computer system.Since the user plane is cut off from the Mobile IP signaling, the userplane can be general-purpose equipment applicable to a system other thanthe Mobile IP. As a result, a cheap product can be provided.

When the mobile node (MN) 2 using the FA care-of address performsposition registration, since the IP address at the IP tunnel endpoint inthe IP tunnel router, being a part of the FA function in the Mobile IPprocedure, and the IP address at the IP tunnel endpoint in the IP tunnelrouter, being a part of the HA function are exchanged, the IP tunnel canbe correctly set in the Mobile IP network in which the control plane andthe user plane are separated.

Second Embodiment

FIG. 5 is a conceptual diagram illustrating the entire operation of theMobile IPv4 network in the second embodiment, and FIG. 6 illustrates anoperation flow of each apparatus at the time of the positionregistration.

In this embodiment, the FA control server 7 a and the IP tunnel router 8a notify the mobile node (MN) 2 of information in the same method as inthe first embodiment. In the second embodiment, the mobile node (MN) 2selects to use the collocated care-of address of the Mobile IPv4 or theMobile IPv6. In this case, the mobile node (MN) 2 creates a positionregistration message including the own IP address of the mobile node(MN) 2 as the endpoint of the IP tunnel, and transmits the message tothe known HA control server 9 (reference numeral 18 in FIG. 5). The HAcontrol server 9 having received the position registration messageobtains the address, being the endpoint of the IP tunnel, in the IPtunnel router 8 b after having stored the IP tunnel information in themessage, in the same method as in the first embodiment. At this time,the HA control server 9 notifies the IP tunnel router 8 b of the IPtunnel endpoint of the opposing mobile node (MN) 2.

The HA control server 9 sets the obtained IP tunnel endpoint address inthe IP tunnel router 8 b in the position registration response messageas a HA address, and transmits the message to the mobile node (MN) 2(reference numeral 19 in FIG. 5). At this point in time, the IP tunnelbetween the mobile node (MN) 2 and the IP tunnel router 8 b (referencenumeral 16 in FIG. 5) is established.

By a series of operation, a user data path via the IP tunnel router 8 bas illustrated in FIG. 6 is constructed.

When the mobile node (MN) 2 using the collocated care-of addressperforms position registration, since the IP address of the mobile node(MN) 2 and the IP address of the IP tunnel endpoint in the IP tunnelrouter, being a part of the HA function are exchanged, the IP tunnel canbe correctly set in the Mobile IP network in which the control plane andthe user plane are separated.

Third Embodiment

FIG. 7 is a conceptual diagram illustrating the entire operation of theMobile IPv4/v6 in the third embodiment.

In the embodiment, the FA control server 7 a is informed of the IPaddress as the default router of the mobile node MN by the IP tunnelrouter 8 a (reference numeral 20 in FIG. 7). This is informed at anytime, when the apparatus of the IP tunnel router 8 a is started up orthe operation status of the IP address changes. Alternatively, the FAcontrol server 7 a may statically hold the IP address as theconfiguration data.

In a path 21 illustrated in FIG. 7, when the FA control server 7 aregularly broadcasts the own address as the FA care-of address, the FAcontrol server 7 a broadcasts the IP address as the default router inthe IP tunnel router 8 a at the same time. The message is also a kind ofthe ICMP message and is a distributed mobile agent advertisement.However, the message also includes the ICMP router advertisementinformation other than the information described in the firstembodiment.

As illustrated in FIG. 3, the mobile node (MN) 2 receives thedistributed mobile agent advertisement and recognizes the sender MAC/IPaddresses as the FA control server 7 a, being the destination of theposition registration signaling. Further, the mobile node MN recognizesthe IP address as the default router from the ICMP router advertisementinformation.

The mobile node MN can respectively recognize the FA control server onthe control plane and the IP tunnel router on the user plane, byreceiving the ICMP router advertisement in the distributed mobile agentadvertisement. However, since the MAC address is unknown as an addressof the IP tunnel router, the mobile node MN needs to resolve the MACaddress from the IP address according to ARP. Particularly, there may bea constraint on Mobile IP in which the home address of the mobile nodeMN cannot be used for ARP. In this case, the mobile node MN using thecollocated care-of address can use the mechanism.

Since, the FA control server notifies the mobile node (MN) 2 of the ownaddress as the FA care-of address and the address in the IP tunnelrouter constituting the FA function as the default router IP address,the mobile node (MN) 2 can respectively recognize the FA control serverand the IP tunnel router. Therefore, a Mobile IP network in which thecontrol plane and the user plane are separated totally from the mobilenode (MN) 2 to the HA can be constructed. Particularly, the mobile node(MN) 2 using the collocated care-of address can use this mechanism.

Fourth Embodiment

FIG. 8 is a conceptual diagram illustrating the entire operation of theMobile IPv4 in the fourth embodiment.

In this embodiment, the IP tunnel router 8 a is informed of the IPaddress of the FA control server, being the care-of address, by the FAcontrol server 7 a (reference numeral 22 in FIG. 8). This is informed atany time, when the apparatus in the FA control server 7 a is started upor the operation status of the IP address changes. Alternatively, the IPtunnel router 8 a may statically hold the IP address as theconfiguration data.

In a path 23 in FIG. 8, when regularly broadcasting the IP address,being the default router, to the mobile node MN, the IP tunnel router 8a broadcasts the address of the FA control server 7 a as the care-ofaddress at the same time. The message is a kind of the ICMP message andis referred to as a distributed ICMP router advertisement. In order toinform the mobile node MN that the storage network is the distributedMobile IP network, a code field value and the like in the message ischanged with respect to a normal ICMP router advertisement. The messagealso includes the mobile agent advertisement information other than theinformation described in the first embodiment. As illustrated in FIG. 3,the mobile node (MN) 2 receives the distributed ICMP routeradvertisement, and recognizes the sender MAC/IP addresses thereof as theIP tunnel router 8 a, being the default router. The mobile node (MN) 2also recognizes the IP address of the FA control server 7 a from themobile agent advertisement information.

The mobile node (MN) 2 can respectively recognize the FA control serveron the control plane and the IP tunnel router on the user plane, byreceiving the mobile agent advertisement in the distributed ICMP routeradvertisement. However, since the MAC address is unknown as the addressof the FA control server, the mobile node MN needs to resolve the MACaddress from the IP address according to the ARP. Particularly, theremay be a constraint on Mobile IP in which the home address of the mobilenode MN cannot be used for the ARP. In this case, the mobile node (MN)using the collocated care-of address can use the mechanism.

Since, the IP tunnel router notifies the mobile node (MN) 2 of the FAcontrol server address as the FA care-of address and the own address asthe default router IP address, the mobile node (MN) 2 can respectivelyrecognize the FA control server and the IP tunnel router. Therefore, aMobile IP network in which the control plane and the user plane areseparated totally from the mobile node (MN) 2 to the HA can beconstructed.

Particularly, the mobile node (MN) 2 using the collocated care-ofaddress can use this mechanism.

Fifth Embodiment

FIG. 9 is a conceptual diagram illustrating the entire operation of theMobile IPv4 in the fifth embodiment, and FIG. 10 illustrates theoperation flow of each apparatus at the time of executing positionregistration.

In this embodiment, the IP tunnel router 8 a regularly broadcasts the IPaddress, being the default router, and the care-of address in the IPtunnel router 8 a, to the mobile node (MN) 2, via a path 24 in FIG. 9,according to the specifications of the normal Mobile IP. This message isa normal mobile agent advertisement message. As illustrated in FIG. 3,the mobile node (MN) 2 receives the mobile agent advertisement, andrecognizes the sender MAC/IP addresses thereof as the normal FA, beingthe destination of the position registration and the destination of theuser packet.

The mobile node (MN) 2 having recognized the IP address of the IP tunnelrouter 8 a as the FA address creates a position registration messageincluding the IP address information of the known HA control server 9,and transmits the message to the MAC/IP addresses of the mobile agentadvertisement sender (reference numeral 25 in FIG. 9).

The IP tunnel router 8 a receives the position registration message,detects that this message is a Mobile IP related message from a UDP portnumber (the UDP port number in the Mobile IP signaling is fixed to 434),and transfers this message to the FA control server 7 (reference numeral29 in FIG. 9). For this transfer, a signaling transfer mechanismspecified between the MGC and MG is used. In the case of the MobileIPv6, the Mobile IP signaling is identified by the option type of theIPv6 receiver option header. The FA control server 7 a handles thetransferred Mobile IP signaling as if it is received from the mobilenode (MN) 2.

The IP tunnel router constituting the virtual FA serves as the FA withrespect to the mobile node (MN) 2, and when having received the MobileIP message from the mobile node (MN) 2, transfers this message to the FAcontrol server. The FA control server having received the Mobile IPmessage from the HA control server transfers this message to the IPtunnel router, and the IP tunnel router delivers this message to themobile node (MN) 2. By this mechanism, a Mobile IP network in which thecontrol plane and the user plane are separated totally from the FA tothe HA can be constructed. The mobile node (MN) 2 can accommodate thenormal Mobile IP node.

Sixth Embodiment

FIG. 11 illustrates the operation flow of each apparatus at the time ofobtaining the address of the HA control server by the mobile node (MN) 2in the Mobile IPv4 according to the sixth embodiment. In thisembodiment, it is assumed that the mobile node (MN) 2 does not know theIP address of the HA control server, and an automatic acquisitionmechanism of the IP address of the HA control server is specified.

The mobile node (MN) 2, which does not know the address of the HAcontrol server creates a position registration message in which thesubnet prefix of the home address and All 0 are set in the home addressregion, according to the specifications of the Mobile IP, and transmitsthis message to the subnet of the HA control server via the FA controlserver.

An edge router existing in the subnet of the HA control serverbroadcasts this message in the subnet. In the present invention, the HAcontrol server captures the broadcast packet, and returns a response ofrejecting the position registration in which the IP address of the HAcontrol server is set.

The mobile node MN receives the rejection response of positionregistration, understands the IP address of the HA control server, andexecutes position registration toward the HA control server.

The HA control server responds (gives a rejection response) to theposition registration of the Mobile IPv4 broadcasted in the HA subnet,thereby informing the mobile node (MN) 2 of the address of the HAcontrol server. Therefore, in the Mobile IPv4 network in which thecontrol plane and the user plane are separated, correspondence to aninstance in which the mobile node (MN) 2 does not know the address ofthe HA control server becomes possible.

Seventh Embodiment

The seventh embodiment assumes a Mobile IPv6 network, in which the FAcontrol server 7 in FIG. 1 is replaced by an AR control server as thenetwork, and the virtual AR is formed of an AR control server and an IPtunnel router 8. Particularly, for the virtual AR, the one that supportsthe Mobile IP function is assumed.

In the seventh embodiment, the AR control server notifies the mobilenode (MN) 2 of the own IP address, like the FA control server in thefirst embodiment. As in the third embodiment, the AR control servernotifies the mobile node MN of the IP address of the IP tunnel router,being the default router, in addition to the own IP address. Further, asin the fourth embodiment, the IP tunnel router notifies the mobile node(MN) 2 of the IP address of the AR control server. As in the fifthembodiment, the Mobile IP message captured by the IP tunnel router istransferred to the AR control server, and the AR control server havingreceived the Mobile IP message from the HA function transmits the MobileIP message to the mobile node (MN) 2 via the IP tunnel router.

In the Mobile IP network in which the control plane and the user planeare separated, the load balancing between the control plane and the userplane becomes possible, thereby enabling independent correspondence toupgrade of signaling and speed-up of the tunnel processing. As a result,an optimized system can be constructed.

Eighth Embodiment

FIG. 12 illustrates the operation flow of each apparatus at the time ofobtaining the HA control server address by the mobile node (MN) 2 in theMobile IPv6 according to the eight embodiment.

The mobile node (MN) 2 that does not know the address of the HA controlserver creates a position registration message in which the subnetprefix of the home address and All 0 are set in the home address region,according to the specifications of the Mobile IP, encapsulates themessage with an anycast address in the subnet of the home address, andtransmits the message to the subnet of the HA control server.

This message is received by an optional router existing in the subnet ofthe HA control server, and the router performs decapsulation, and thismessage is broadcasted in the subnet. In the present invention, the HAcontrol server captures the broadcasted packet, and returns a rejectionresponse of position registration in which the IP address of the HAcontrol server is set.

The mobile node (MN) 2 receives the rejection response of positionregistration, understands the IP address of the HA control server, andexecutes position registration toward the HA control server.

The mobile node (MN) 2 can recognize the FA control server and the IPtunnel router respectively independently. Therefore, a Mobile IP networkin which the control plane and the user plane are separated totally fromthe mobile node (MN) 2 to the HA can be constructed.

In the Mobile IP network in which the control plane and the user planeare separated, the load balancing between the control plane and the userplane becomes possible, thereby enabling independent correspondence toupgrade of signaling and speed-up of the tunnel processing. As a result,an optimized system can be constructed.

In the Mobile IPv4 network in which the control plane and the user planeare separated, correspondence to an instance in which the mobile node(MN) 2 does not know the address of the HA control server becomespossible.

According to the present invention, the mobile node (MN) 2 can recognizethe FA control server and the IP tunnel router respectivelyindependently. Therefore, a Mobile IP network in which the control planeand the user plane are separated totally from the mobile node (MN) 2 tothe HA can be constructed.

In the Mobile IP network in which the control plane and the user planeare separated, the load balancing between the control plane and the userplane becomes possible, thereby enabling independent correspondence toupgrade of signaling and speed-up of the tunnel processing. As a result,an optimized system can be constructed.

INDUSTRIAL APPLICABILITY

The mobility management method according to the distributed Mobile IP ofthe present invention is useful for mobility management in the mobilepacket communication, and is particularly suitable for the Mobile IPv4or Mobile IPv6 network.

1. A mobility management system using a distributed Mobile IP, in a Mobile IP network which allows a mobile node while moving to hold a current communication session, comprising: a foreign agent control server that is located in a first subnet where the mobile node is located, performs Mobile IP signaling; a first IP tunnel router that is located in, the first subnet, and performs IP tunnel transfer; a home agent control server that is located in a second subnet where the mobile node is located, and performs Mobile IP signaling; and a second IP tunnel router that is located in the second subnet, and performs IP tunnel transfer, wherein the foreign agent control server and the first IP tunnel router constitute a virtual foreign agent, and the home agent control server and the second IP tunnel router constitute a virtual home agent.
 2. The mobility management system according to claim 1, wherein the foreign agent control server transmits to the mobile node a message indicating an IP address of the foreign agent control server, and the first IP tunnel router transmits to the mobile node a message indicating an IP address of a default router.
 3. The mobility management system according to claim 1, wherein the foreign agent control server, when receiving a first request for position registration from the mobile node, determines a first IP tunnel endpoint in the first IP tunnel router, and transmits a second request including the first request and an IP address of the first IP tunnel endpoint to the home agent control server, the home agent control server determines a second IP tunnel endpoint in the second IP tunnel router, sets the first IP tunnel endpoint and the second IP tunnel endpoint into the second tunnel router, and transfers to the foreign agent control server a response to the second request, and the foreign agent control server sets the second IP tunnel endpoint into the first IP tunnel router, and transfers to the mobile node the response.
 4. The mobility management system according to claim 1, wherein the home agent control server receives a request including an IP address of a first IP tunnel endpoint being the mobile node, determines a second IP tunnel endpoint in the second IP tunnel router, and transmits to the mobile node a response to the request.
 5. The mobility management system according to claim 1, wherein the foreign agent control server transmits to the mobile node a message indicating an IP address of the foreign agent control server and an IP address of the second IP tunnel router serving as a default router.
 6. The mobility management system according to claim 1, wherein the first IP tunnel router serves as a default router for the mobile node, and transmits to the mobile node a message indicating an IP address of the default router and an IP address of the foreign agent control server.
 7. The mobility management system according to claim 1, wherein the first IP tunnel router transfers, when receiving a first Mobile IP message transmitted by the mobile node, the first Mobile IP message to the foreign agent control server, the foreign agent control server transfers, when receiving a second Mobile IP message transmitted by the home agent control server, the second Mobile IP message to the first IP tunnel router, and the first IP tunnel router transfers the second Mobile IP message to the mobile node.
 8. The mobility management system according to claim 1, wherein the mobile node transmits a request for position registration to the foreign agent control server so that the request is broadcasted over the second subnet, the home agent control server transmits to the foreign agent control server a response to the request, the response including an IP address of the home agent control server and indicating rejection to the position registration, and the foreign agent control server transfers to the mobile node the response.
 9. The mobility management system according to claim 1, wherein the Mobile IP network is an IPv4 network.
 10. A mobility management system using a distributed Mobile IP, in a Mobile IP network which allows a mobile node while moving to hold a current communication session, comprising: an access router control server that is located in a first subnet where the mobile node is located, performs Mobile IP signaling; a first IP tunnel router that is located in the first subnet, and performs IP tunnel transfer; a home agent control server that is located in a second subnet where the mobile node is located, and performs Mobile IP signaling; and a second IP tunnel router that is located in the second subnet, and performs IP tunnel transfer, wherein the access router control server and the first IP tunnel router constitute a virtual access router, and the home agent control server and the second IP tunnel router constitute a virtual home agent.
 11. The mobility management system according to claim 10, wherein the access router control server transmits to the mobile node a message indicating an IP address of the access router, and the first IP tunnel router transmits to the mobile node a message indicating an IP address of a default router.
 12. The mobility management system according to claim 10, wherein the access router control server transmits to the mobile node a message indicating an IP address of the foreign agent control server and an IP address of the second IP tunnel router serving as a default router.
 13. The mobility management system according to claim 10, wherein the first IP tunnel router serves as a default router for the mobile node, and transmits to the mobile node a message indicating an IP address of the default router and an IP address of the access router control server.
 14. The mobility management system according to claim 10, wherein the first IP tunnel router transfers, when receiving a first Mobile IP message transmitted by the mobile node, the first Mobile IP message to the access router control server, the access router control server transfers, when receiving a second Mobile IP message transmitted by the home agent control server, the second Mobile IP message to the first IP tunnel router, and the first IP tunnel router transfers the second Mobile IP message to the mobile node.
 15. The mobility management system according to claim 10, further a router located in the second subnet, wherein the mobile node transmits a request for position registration to the foreign agent control server so that the request is broadcasted over the second subnet, the request being encapsulated with an anycast address in the second subnet, the router receives and decapsulates the request, and broadcasts the request decapsulated over the second subnet, the home agent control server transmits to the router a response to the request broadcasted, the response including an IP address of the home agent control server and indicating rejection to the position registration, and the router transfers to the mobile node the response.
 16. The mobility management system according to claim 10, wherein the Mobile IP network is an IPv6 network. 